The present invention relates to plastic shopping bags having integral handle portions, and to a novel method for manufacturing such bags.
Various plastic bag structures, and methods of manufacturing the same, have been suggested heretofore wherein the bags are provided with handles located at the mouth of the bag and having a hole therein to facilitate carrying of the bag or to suspend the bag from a rack or hanger. It has also been suggested heretofore that such bags can be formed by the provision of appropriate longitudinal and transverse seam lines in an elongated length of molded plastic tubing, which seam lines serve to sever individual bags from a length of such tubing; and has additionally been suggested heretofore that selected portions of such a bag, including the handle portion thereof, may be reinforced by gluing reinforcement material onto portions of the bag, or by increasing the gauge of selected portions of the tube, at those regions where it is desired to provide additional strength in the finished bag.
The attachment of separate strips of reinforcement material to a plastic tube, and/or the extrusion of heavier gauge portions in the plastic tube to provide such reinforcement, ordinarily require comparatively complex and expensive machinery, and the resultant bags tend to be comparatively expensive. Moreover, known bag manufacturing techniques which contemplate the provision of such heavier gauge strips of material at portions of the bag have been such that the heavier gauge material ordinarily intersects those portions of the tube wherein the transverse seam lines, or side seams of the bag, are to be formed; and this in turn produces difficulties during the seaming of the bag edges since the transverse seam lines extend across film layers of differing thicknesses.
More particularly, it has been suggested heretofore that plastic shopping bags can be fabricated by providing a comparatively wide plastic film tubing as a starting material, said tubing having a pair of reinforcement strips formed on the opposing sides thereof, e.g., during the extrusion of the plastic tubing. The reinforced portion of the tubing is severed longitudinally by a cutting line of wave configuration which has a wavelength that corresponds to the width of the bag, and individual bags are therafter cut from the starting tubing by providing transverse seam lines which intersect the wavelike cutting line. In this known method, the wavelike and transverse cutting lines are so located relative to one another and to the reinforcement strip in the bag that the reinforcement extends across the side seams of the bag; and this produces problems during the seaming of the bag edges since, at these locations, differing film thicknesses exist. The thicker plastic film section is not as easily seamable as the thinner sections, which makes it difficult to produce consistent side seams in rapid mass production. Moreover, the thickened region which is provided in the center of the plastic tubing impairs the reeling of such tubing as may be desired in a mass production technique, and makes it difficult to keep the plastic tubing on such reels.
The present invention obviates these disadvantages of the prior art, and provides an improved bag and manufacturing technique which achieves the desired reinforcement in the handle portion of the bag, but which does so in a fashion which significantly reduces the costs of production and of the resulting bags. A bag manufactured according to the present invention permits the side seams to be achieved more quickly than has been possible heretofore since the side seams always occur on film sheet layers of predetermined constant thickness. Moreover, the techniques and resulting bags of the present invention achieve a saving of plastic raw material, a factor which has significance in the larger scale production of inexpensive plastic shopping bags.